[MacPorts] #55497: py-cairo: use a release download

[MacPorts]

#55497: py-cairo: use a release download
-------------------------+------------------------
 Reporter:  ryandesign   |      Owner:  seanfarley
     Type:  enhancement  |     Status:  new
 Priority:  Normal       |  Milestone:
Component:  ports        |    Version:
 Keywords:               |       Port:  py-cairo
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 The py-cairo portfile uses the github portgroup's default behavior of
 downloading an automatically-generated tarball.

 But the pycairo project offers
 [https://github.com/pygobject/pycairo/releases release downloads]. So at
 the next opportunity (i.e. when the port is updated to the next version)
 the port should switch to such a download, by adding `github.tarball_from
 releases` to the portfile.

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Ticket URL: <https://trac.macports.org/ticket/55497>
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